Tubular heat lamp having integral gettering means

ABSTRACT

The helical filament coil of a tubular infrared type electric lamp is suspended within the quartz envelope by a series of spaced tungsten-wire spiral supports and gettering of gaseous impurities within the lamp is achieved by a separate member of tantalum (or other material) that is locked in contact with and is thus heated by the end of the filament coil. The gettering component is of elongated configuration and so arranged relative to the end of the filament coil and its attached lead-in wire that the gettering component extends along the gradienttemperature zone established at that location when the filament is energized - thereby insuring that at least a portion of the gettering material is heated to a predetermined temperature (preferably from about 600* to 1,000*C in the case of tantalum).

United States Patent [1 1 Martin et al.

[ July 24, 1973 TUBULAR HEAT LAMP HAVING INTEGRAL GETTERING MEANS [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: Oct. 6, 1971 [21] Appl. No.: 186,968

[52] US. Cl 313/178, 313/179, 313/279 [51] Int. Cl. I-I0lk 1/54 [58] Field of Search 313/222, 178, 273,

[56] References Cited UNITED STATES PATENTS 3,240,975 3/1966 English et al. 313/222 2,444,423 7/1948 Braunsdorff 313/178 3,132,278 5/1964 Collins et al 3131178 3,644,773 2/1972 Coaton et al. 313/179 X FOREIGN PATENTS OR APPLICATIONS 457,759 4/1970 Japan Primary Examiner-Palmer C. Demeo Att0rneyA. T. Stratton, D. S. Buleza et al.

[57] ABSTRACT The helical filament coil of a tubular infrared type electric lamp is suspended within the quartz envelope by a series of spaced tungsten-wire spiral supports and gettering of gaseous impurities within the lamp is achieved by a separate member of tantalum (or other material) that is locked in contact with and is thus heated by the end of the filament coil. The gettering component is of elongated configuration and so arranged relative to the end of the filament coil and its attached lead-in wire that the gettering component extends along the gradient-temperature zone established at that location when the filament is energized thereby insuring that at least a portion of the gettering material is heated to a predetermined temperature (preferably from about 600 to 1,000C in the case of tantalum).

8 Claims, 7 Drawing Figures TUBULAR HEAT LAMP HAVING INTEGRAL GETTERING MEANS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric lamps and has particular reference to an improved infraredradiation generating type incandescent lamp that is adapted for use as a concentrated heat source.

2. Description of the Prior Art Compact infrared-generating lamps are well known in the art and are widely used as concentrated sources of heat in various manufacturing and testing applications. Such heat lamps are made in various wattage ratings and generally consist of a helical filament of coiled tungsten wire that is suspended within a tubular envelope of quartz (or other material that has a high softening point) which contains a suitable inert fill gas, such as argon or the like.

The present practice is to suspend the filament in centralized position within the envelope by means of a series of spaced discs that are fabricated from tantalum and thus serve both as filament supports and getter means for removing the trace amounts of contaminating gases that are present in the fill gas at initial lightup and which evolve within the lamp during use. An infrared-radiation generating lamp having a tungsten filament that is supported by such tantalum discs (or by spiral-shaped tantalum wire supports) is disclosed in U.S. Pat. No. 2,864,025 issued Dec. 9, 1958 to A. G. Foote et al.

While the prior art lamp designs were satisfactory from an operational standpoint, their manufacturing cost was rather high since a relatively large number of supports are required and it is difficult and timeconsuming to attach them to the coiled filament and firmly anchor them in place. The number of discs used in a particular lamp depends, of course, on the lamp length and can vary from six discs in the case of a 375 watt lamp to as many as forty-three in a 3,800 watt lamp.

SUMMARY OF THE INVENTION Briefly, the present invention overcomes the aforementioned manufacturing and cost drawbacks by replacing the tantalum support discs with tungsten wire spirals and employing a separate gettering component that is attached at a strategic location to one end of the filament coil. The tungsten spiral supports are identical to those employed in tungsten-halogen type lamps and can thus be efficiently and automatically attached to the filament with the same equipment. The filamentsupport assemblies for both types of lamps are thus identical in this respect. The resulting standardization greatly simplifies the manufacturing operation and reduces the cost of the infrared lamps.

The gettering component is attached directly to the end of the filament coil where it joins the lead-in wire, or it is locked in place on the lead-in wire itself. In either case, it extends along the gradient-temperature zone created at the end of the filament when the lamp is energized. At least a portion of the gettering component is thus heated to a temperature at which the getter functions most effectively as a purging agent. The amount of gettering material required per lamp is accordingly markedly reduced, even though a gettering component is preferably used at each end of the filament.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the invention will be obtained from the exemplary embodiment shown in the accompanying drawings, wherein:

FIG. 1 is an elevational view of a representative infrared-radiation generating type electric lamp which embodies the present invention;

FIG. 2 is an enlarged fragmentary perspective view of a portion of the filament coil and the associated tungsten-wire spiral support;

FIG. 3 is an enlarged side elevational view of one end of the filament coil and attached getter and lead-in conductor components employed in the lamp shown in FIG. 1;

FIGS. 4-6 are similar views of modified getter structures according to the invention; and,

FIG. 7 is a fragmentary plan view of still another type of getter-filament assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown a typical infrared type electric lamp 10 which has the usual tubular envelope 12 that is composed of a suitable radiation-transmitting high melting point material such as quartz (or a quartzlike material such as Vycor glass that contains about 96% quartz and thus also consists essentially of fused silica) and contains a longitudinally-extending helical filament 14 of coiled tungsten wire and a suitable insert gas such as argon, krypton or xenon at a pressure of about 1 atmosphere. Each end of the envelope 12 is hermetically closed by a press seal 16 and the lamp 10 is energized by means of suitable lead-in assemblies that consist of an outer lead 17, a joined molybdenum foil 18 that is embedded in the respective press seals and is welded to an inner lead-in conductor 19 of refractory metal (such as molybdenum) which is fastened to the proximate end of the filament coil 14. As will be noted, the filament coil 14 is held in centralized suspended position within the envelope 12 by a series of spaced support members 20 that are attached to the filament and extend toward the inner wall of the envelope.

As shown more particularly in FIG. 2, each of the aforementioned support members 20 in accordance with the present invention consists of a spiral of tungsten wire that is dimensioned to nestingly engage the envelope 12 and is fastened to the filament coil 14 by tightly winding the end of the tungsten wire around the coil. Tungsten-wire spiral supports of this type are used in halogen-cycle incandescent lamps and a method and apparatus for automatically forming and attaching such supports to a helical filament are disclosed in detail in U.S. Pat. No. 3,270,781 issued Sept. 6, 1966 to W. L. Brundige.

Returning to FIG. 1, it will be noted that each end of the filament coil 14 is provided with a getter component which, in this particular embodiment, comprises a hollow sleeve 22 of tantalum that is locked in place by a suitable retaining means such as a short transverse stub wire 24 of molybdenum (or other refractory metal) that is spot-welded to the inner lead-in wire 19.

As shown more particularly in FIG. 3, the tantalum sleeve 22 is held in abutting engagement with the end turn of the filament coil 14 by the stub wire 24 which, in turn, is seated against the opposite end of the sleeve. The getter component 22 is thus locked in direct physical contact with the filament 14 in telescoped overlying relationship with the lead-in wire 19 and extends along the gradient-temperature zone" T that extends from the stub wire 24 to approximately the end of the inner lead-in wire 19 which is inserted into and anchored to the filament coil 14. As is well known in the art, the juncture of the lead-in wire 19 and filament coil 14 is customarily achieved by serrating one end of the leadin wire to provide a series of uniformly spaced notches and then threadably inserting the wire into tight engagement with the end turns of the filament. Hence, when the filament coil 14 is energized and incandesces, the heat sink effect of the attached lead 19 causes the temperature to progressively decrease as one proceeds along the gradient-temperature zone or site T from the inner tip of the lead-in wire 19 to the stub wire 24. Since the sleeve 22 extends along this site, at least a portion of the tantalum will be heated to a temperature at which it is most effective as a gettering material.

As is well known, tantalumis an excellent getter for hydrogen, nitrogen and oxygen and operates most effectively within a temperature range of from about 600C to 1,000C. However, care should be taken that that temperature of the sleeve 22 at its hottest point is maintained below about 1,500C since tantalum apparently re-evolves and releases hydrogen and oxygen at this temperature.

Thus, by placing and locking the elongated gettering component 22 in the aforementioned gradienttemperature site T produced within the energized lamp and correlating the physical location of the gettering component with the nominal wattage rating of the lamp 10, the operating temperature of the body of gettering material can readily be controlled and maintained within the limits at which the particular gettering material operates most effectively.

Tests have shown that the tantalum sleeve arrangement illustrated in FIG. 3 in which the end of the sleeve 22 is seated against the end of the filament coil 14 provides excellent results in the case of infrared lamps having a nominal wattage rating of 500 watts and so-called T3 type envelopes (9.5 millimeters OD) The sleeves in this case were rolled from tantalum strips that were about 0.07 mm. thick, 6 mm. wide and 7 mm. long and were rolled into hollow sleeves having an inside diameter of 1.5 mm.

In the case of lower wattage lamps (375 watt lamps for example), the above-described abutting contact between the filament coil and getter component may be insufficient to raise the gettering material to the required temperature. The embodiment shown in FIG. 4 is accordingly preferably used in such lower wattage lamps and, as shown, employs a tantalum sleeve 22a that is larger in diameter and tightly encloses and contacts the end segment of the filament coil 14a that is coupled to the inner lead wire 19a. The opposite end of the sleeve 22a is constricted, as by crimping, so that it firmly grips the inner lead 19a and (as in the previous embodiment) is seated against the transverse stub wire 24a. The sleeve 22a is thus positioned so that it extends to approximately the hot end of the gradienttemperature zone T.

The getter component is not limited to sleeve-like members but can take various other forms. As shown in FIG. for example, it can consist ofa length of tanta lum wire that is tightly wound around the end of the filament coil 14b to provide a winding or helix 26 that is securely locked in overlapped relationship with the fila- 5 ment and extends along the gradient-temperature zone Alternatively, as illustrated in FIG. 6, the getter component can comprise a flat strip 28 of suitable gettering material such as tantalum that is fastened (as by welding) to one or more of the end turns of the filament coil 14c and thus provides a flaglike structure that extends along the gradient-temperature zone T.

The getter component can also be fabricated from other gettering materials, such as zirconium, or an alloy of tantalum and tungsten for example. An alloy of 92 /2 percent tantalum 7% percent tungsten has given good results. It can also comprise an elongated composite structure 30, such as that shown in FIG. 7, wherein the gettering material consists of a coating 32 (an alloy of zirconium and aluminum, for example) on a flat metal substrate of iron or other suitable metal which is spot-welded to the filament coil 14d and ex tends into and along the gradient-temperature zone T. Preferably, the substrate is welded to the filament turns along getter-free borders B provided at each end of the flag-like component.

We claim as our invention:

1. In an electric incandescent lamp having a prede termined wattage rating and a sealed tubular radiationtransmitting envelope that contains a filament coil of tungsten wire, the combination comprising;

a rigid lead-in conductor that is embedded in a sealed end portion of said envelope and extends into and is fastened to the proximate end of said filament coil and together therewith constitutes an elongated electrical joint that provides a gradienttemperature site within the lamp, when the latter is operated at its rated wattage, that extends from the end of said lead-in conductor enclosed by the filament coil to a point on said conductor which is located beyond the end of said coil and is spaced inwardly from the associated sealed end portion of said envelope,

means holding said filament coil in centralized longitudinally-extending position within said envelope comprising at least one support member of refractory metal wire that is coupled to a medial part of the filament coil and is nestingly engageable with the inner wall of said envelope, and

means for purging gaseous impurities within the lamp comprising an elongated gettering component that is locked in physical contact with said filament coil and extends along said gradient-temperature site, said gettering component being of such configura tion that at least a portion thereof overlies part of the filament coil and is thereby directly heated to a temperature within a predetermined range when the lamp is operated at said wattage rating.

2. The combination of claim 1 wherein said gettering component comprises a tantalum member and said temperature range is from about 600 to l,000C.

3. The combination of claim 1 wherein;

said lamp comprises an infrared-generating lamp that has a fused-silica envelope of circular cross-section which is closed at each end by a hermetic seal,

said lead-in conductor comprises a refractory metal wire that is embedded in one of said seals and is mechanically interlocked with the proximate end of the filament coil, and

said filament-holding means comprises a plurality of tungsten wire supports of arcuate configuration that are wound about and anchored to the filament coil at spaced intervals along its length.

4. The combination of claim 3 wherein;

said lead-in wire is composed of molybdenum, and

said locking means comprises a stub wire that is welded to and extends transversely relative to said lead-in wire.

5. The combination of claim 3 wherein;

said gettering component comprises a tantalum sleeve, one end whereof is disposed in overlying telescoped relationship with the end of the filament coil and the opposite end whereof is constricted and in snug-fitting telescoped relationship with the adjoining part of said lead-in wire, and

said tantalum sleeve is locked in such position by means that is fastened to said lead-in wire and abuttingly engages the outermost end of said sleeve.

6. The combination of claim 3 wherein said gettering component comprises a wire winding that encircles and grips a part of the filament coil.

8. The combination of claim 3 wherein said gettering component comprises a metal strip that is welded to at least one turn of the filament coil.

8. The combination of claim 3 wherein said gettering component comprises a coating on a metal substrate of strip-like configuration that is welded to at least one turn of the filament coil. 

2. The combination of claim 1 wherein said gettering component comprises a tantalum member and said temperature range is from about 600* to 1,000*C.
 3. The combination of claim 1 wherein; said lamp comprises an infrared-generating lamp that has a fused-silica envelope of circular cross-section which is closed at each end by a hermetic seal, said lead-in conductor comprises a refractory metal wire that is embedded in one of said seals and is mechanically interlocked with the proximate end of the filament coil, and said filament-holding means comprises a plurality of tungsten wire supports of arcuate configuration that are wound about and anchored to the filament coil at spaced intervals along its length.
 4. The combination of claim 3 wherein; said lead-in wire is composed of molybdenum, and said locking means comprises a stub wire that is welded to and extends transversely relative to said lead-in wire.
 5. The combination of claim 3 wherein; said gettering component comprises a tantalum sleeve, one end whereof is disposed in overlying telescoped relationship with the end of the filament coil and the opposite end whereof is constricted and in snug-fitting telescoped relationship with the adjoining part of said lead-in wire, and said tantalum sleeve is locked in such position by means that is fastened to said lead-in wire and abuttingly engages the outermost end of said sleeve.
 6. The combination of claim 3 wherein said gettering component comprises a wire winding that encircles and grips a part of the filament coil.
 8. The combination Of claim 3 wherein said gettering component comprises a metal strip that is welded to at least one turn of the filament coil.
 8. The combination of claim 3 wherein said gettering component comprises a coating on a metal substrate of strip-like configuration that is welded to at least one turn of the filament coil. 